[Objective] The characteristics of the widths, depths, width-depth ratios, profiles, and wall gradients of rills on a mollisol hillslope were analyzed to provide a scientific reference for controlling rill erosion on slope croplands in the Chinese mollisol region.[Methods] Inflow scour experiments with a 1 L/(min·m²) inflow rate were conducted over 60 min under different typical slope gradients (5° and 10°) in natural runoff plots.[Results] ① The rill profiles of the mollisol hill slope were mainly “U” shaped and the mean rill width-depth ratios ranged from 2.3 to 4.9. ② As the slope gradient increased, the undercut erosion of the rills exceeded that of the collapse erosion of the side-walls, which induced a decrease in the rill width-depth ratio and a variation in the rill profiles from a “wide and shallow type” to a “deep and narrow type”. ③ The mean rill width-depth ratios of the upper, middle, and lower hillslope positions were 2.7, 1.6, and 5.4, respectively. This reveals that the rill profile characteristics transformed from the “wide and shallow type” to the “deep and narrow type”, and then to the “wide and shallow type” from the upper hillslope to the lower hillslope. ④ The rill wall gradients of the mollisol hillslope mainly ranged from 37.7° to 85.2°, and increased with an increase in the slope gradient. The rill wall gradients of the middle hillslope were greater than those of the upper and lower hillslopes.[Conclusion] It is much more important to control rill development in the middle parts of relatively steep hillslopes than other parts; this is beneficial for alleviating rill erosion in the mollisol region of China.